Identification of cerebral neurons and glial cell types inducing heat shock protein Hsp70 following heat stress in the rat

Abstract

Heat shock proteins were recently recognized as molecular chaperones that besides their chaperoning function were also involved in processes of cell death and survival. Many types of neural cells were reportedly capable of expressing heat shock protein Hsp70 following heat stress in vitro. However, identification of cell types inducing Hsp70 protein in the hyperthermic brain is not clear. In this study, cerebral Hsp70 distribution was evaluated in anesthetized adult rats (urethane, 1.5 g/kg, i.p.) subjected to short-term hyperthermia (41.5 °C for 30 min). Detection of Hsp70 was achieved by an ABC technique in vibratome or paraffin sections combined with specific markers of glial cell types. Hsp70 appeared by 90 min, mainly in glial and vascular cells, with enhanced immunostaining by 4 h following hyperthermia. Higher numbers of Hsp70-positive cells were detected in the white matter and diencephalic region than in the cerebral cortex, especially over the shorter interval. Hsp70 was localized in many oligodendrocytes, double-labeled with lectin GSII, and some vessels. Microglia showed apparently less Hsp70/OX-42 double-labeled cells than the previous two cell types. In contrast, only a few Hsp70-stained cells were positive for astrocyte marker GFAP. In addition to glial/vascular Hsp70 staining, neuronal Hsp70 induction was observed only in discrete regions including the paraventricular, supraoptic, suprachiasmatic and other hypothalamic nuclei, and in amygdala. Prevailing heat-stress expression of Hsp70 in oligodendrocytes and vascular cells might render them less susceptible to the consequences of other types of cell stress and could be exploited to increase selectively their survival in pathological situations.